This invention relates to water pumps and belt tensioners in general, and specifically to a combined water pump and belt tensioner.
Vehicle engine coolant pumps, generally referred to as water pumps, have a housing secured to the engine block and a pump shaft rotatably supported by a ball or roller bearing within the pump housing. An impeller is fixed to the inner end of the pump shaft, while the outer end extends out of the housing and and has a pulley fixed thereto. A crankshaft driven belt, generally referred to as a fan belt, drives the pump shaft pulley and the pump shaft pulley drives the pump shaft. The belt loads seen by the water pump shaft bearing are large, and generally require a heavy and expensive bearing.
The fan belt is often a long, serpentine belt that powers many other vehicle mounted accessories in addition to the water pump. Consequently, it is highly subject to length change, especially stretch, and some sort of tensioner is needed to maintain proper tension in the fan belt as its length changes so as to maintain proper frictional contact between the belt and the various pulleys that it wraps. The tensioner is typically a structure separate from the accessories, consisting of a swinging arm with a tensioner pulley that is spring loaded into a run of the belt. Tensioners are generally heavy and expensive, as well as somewhat bulky.